<template>
    <div class="music-list">
        <div class="back" @click="back">
            <i class="icon-back"></i>
        </div>
        <h1 class="title" >{{title}}</h1>
        <div class="bg-image"  :style="bgStyle" ref='bgImage'>
            <div class="play-wrapper">
              <div ref="playBtn" v-show="songs.length>0" class="play">
                <i class="icon-play"></i>
                <span class="text">随机播放全部</span>
              </div>
            </div>
            <div class="filter"  ref="filter"></div> 
        </div>
        <div class="bg-layer" ref="layer"></div>
        <scroll :data="songs" class="list" ref="list" :listen-scroll="listenScroll" :probe-type="probeType" @scroll="scroll"> 
          <div class="song-list-wrapper">
            <song-list :songs="songs"></song-list>
          </div>
          <div v-show="!songs.length" class="loading-container">
            <loading></loading>
          </div>

        </scroll>
        
        
       
    </div>   
</template>
<script>
import Scroll from 'base/scroll/scroll'
import SongList from 'base/song-list/song-list'
import {prefixStyle} from 'common/js/dom'
import Loading from 'base/loading/loading'
const RESERVED_HEIGHT=40
const transform=prefixStyle('transform')
const backdrop=prefixStyle('backdrop-filter')


export default {
    data(){
      return{
        scrollY:0
      }
    },
    created(){
      this.probeType=3
      this.listenScroll=true
    },
    components:{
      Scroll,
      SongList,
      Loading
    },
    props:{
      bgImage:{
        type:String,
        default:""
      },
      songs:{
        type:Array,
        default:[]
      },
      title:{
        type:String,
        default:""
      }
    },
    computed:{
      bgStyle(){
        return `background-image:url(${this.bgImage})`
      }
    },
    mounted(){
      this.imageHeight=this.$refs.bgImage.clientHeight
      this.minTransaltey=-this.imageHeight+RESERVED_HEIGHT
      this.$refs.list.$el.style.top=`${ this.imageHeight}px`
    },
    methods:{
      scroll(pos){
        this.scrollY=pos.y
      },
      back(){
        this.$router.back()
      }
    },
    watch:{
      scrollY(newY){
        let translateY=Math.max(this.minTransaltey,newY)
        let scale=1
        let zIndex=0
        let blur=0
        const percent=Math.abs(newY/this.imageHeight)
        if(newY>0){
          scale=1+percent
          zIndex=10
        }else{
          blur=Math.min(20,percent*20)
        }
        this.$refs.layer.style[ transform]=`translate3d(0,${translateY}px,0)`
        this.$refs.filter.style[backdrop]=`blur(${blur}px)`
        if(newY<this.minTransaltey){
          zIndex=10
          this.$refs.bgImage.style.paddingTop=0
          this.$refs.bgImage.style.height=`${RESERVED_HEIGHT}px`
          this.$refs.playBtn.style.display="none"
        }else{
           this.$refs.bgImage.style.paddingTop='70%'
          this.$refs.bgImage.style.height=0
  this.$refs.playBtn.style.display=""
        }
        this.$refs.bgImage.style[ transform]=`scale(${scale})`
        this.$refs.bgImage.style.zIndex=zIndex
        

      }

    }
}
</script>
<style lang="stylus" scoped>
  @import "~common/stylus/variable"
  @import "~common/stylus/mixin"
  
.music-list
    position: fixed
    z-index: 100
    top: 0
    left: 0
    bottom: 0
    right: 0
    background: $color-background
    .back
      position absolute
      top: 0
      left: 6px
      z-index: 50
      .icon-back
        display: block
        padding: 10px
        font-size: $font-size-large-x
        color: $color-theme
    .title
      position: absolute
      top: 0
      left: 10%
      z-index: 40
      width: 80%
      no-wrap()
      text-align: center
      line-height: 40px
      font-size: $font-size-large
      color: $color-text
    .bg-image
      position: relative
      width: 100%
      height: 0
      padding-top: 70%
      transform-origin: top
      background-size: cover
      .play-wrapper
        position: absolute
        bottom: 20px
        z-index: 50
        width: 100%
        .play
          box-sizing: border-box
          width: 135px
          padding: 7px 0
          margin: 0 auto
          text-align: center
          border: 1px solid $color-theme
          color: $color-theme
          border-radius: 100px
          font-size: 0
          .icon-play
            display: inline-block
            vertical-align: middle
            margin-right: 6px
            font-size: $font-size-medium-x
          .text
            display: inline-block
            vertical-align: middle
            font-size: $font-size-small
      .filter
        position: absolute
        top: 0
        left: 0
        width: 100%
        height: 100%
        background: rgba(7, 17, 27, 0.4)
    .bg-layer
      position: relative
      height: 100%
      background: $color-background
    .list
      position: fixed
      top: 0
      bottom: 0
      width: 100%
      background: $color-background
      .song-list-wrapper
        padding: 20px 30px
      .loading-container
        position: absolute
        width: 100%
        top: 50%
        transform: translateY(-50%)
</style>


